Polysaccharide-based composition and its use

ABSTRACT

A polysaccharide-based composition, characterized by comprising or essentially consisting of: 
     at least a first component a) excluding galactane constituted by a substituted β-1,4-linked glycan which is dissolvable in water of a certain temperature and which has a molecular weight (Mw) of ≧5·10 4  Daltons, preferably≧10 5  Daltons, particularly ≧10 6  Daltons, and 
     at least a second component b), also excluding galactans, constituted by a substituted β-1,4-linked glycan which is more difficult to dissolve than said first component at said temperature, or is agar or a carrageenan; 
     the use of the composiiton above as a: 
     a) means for reducing friction, 
     b) means for facilitating removal of undesired contamination from surfaces, such as graffiti, scrawl, soot etc., 
     c) means for preserving moisture, 
     d) protective surface coverage, 
     e) packaging material, 
     f) slow release matrix or coating for drugs; 
     a body in solid phase having a surface intended for contact with a liquid and for relative movement between surface and liquid, said surface being coated with a solid film essentially consisting of such a composition; and 
     a method for the removal of undesired contamination on a surface.

The present invention relates to a polysaccharide-based composition, itsseveral uses, a solid phase body covered by a film essentiallyconsisting of such composition, and a method of removing undesiredcontamination on a surface.

Although the present invention originates from scientific researchaiming at reducing the energy loss at relative movement, morespecifically reducing the friction between a solid body and a liquidcontacting such body, the invention is in fact applicable to a multitudeof uses in addition to such friction-reducing means, which will be madeclear in the following disclosure. However, at the outset, the inventionwill be somewhat outlined against the background of the problem ofreducing the friction between a solid body and a liquid contacting suchbody at relative movement between body and liquid.

At relative movement between a solid body and a liquid, for examplewater, a layer of the liquid adheres to the solid body. This layer, theviscous boundary layer, has a thickness of 20 microns at laminar flowbut can at turbulent flow reach a thickness of 1%-2% of the waterlinelength. In the viscous boundary layer the relative movement speedincreases from zero to the actual speed. The surface friction developsand acts in the viscous boundary layer.

It is known since long that polymers dissolved in the liquid phase canreduce surface friction between liquid and solid body in concentrationsfrom some ppm:s and more. Friction reductions of up to 80% have beenmeasured at a polymer concentration of 200 ppm.

The experiments performed up to now are based on adding polymers to themobile liquid phase, the polymer progressively entering by diffusioninto the viscous boundary layer. Since the friction-reducing effect ofthe polymer acts in the viscous boundary layer the polymer concentrationof said layer is decisive for the degree of reduction of the friction.In order to reduce surface friction on objects moving in water,experiments using different types of release, for example throughnozzles, have shown that unrealistically large quantities of polymershave to be added in order that reduction of the friction shall beattained. This is not surprising since the polymers using this releasetechnique at laminar flow will be added to the bypassing aqueous phaseand thereby removed from the surface of the object and its viscousboundary layer.

One object of the present invention is to provide a technique forreducing the friction between a solid body and a liquid whereby thedisadvantages of the known techniques are eliminated and a substantialreduction of the friction will be obtained. Thus, on the one hand, theinvention aims at substantial reduction of the quality of polymer thathas to be added and, on the other hand, while using a substantiallyreduced quantify of the polymer the invention provides for substantialreduction of the friction.

To attain this object of the present invention there is provided apolysaccharide-based composition comprising at least two components, oneof which has a higher dissolvability in water at a certain temperaturethan the other one at the same temperature.

Another object of the invention is to provide techniques capable offacilitating removal of undesired contamination from surfaces, toprovide means for preserving moisture, to provide for protective surfacecoverage, to provide packaging materials, and to provide means forobtaining slow release for drugs.

The invention also covers bodies in solid phase having a surface coatedwith a solid film essentially consisting of a composition as outlinedabove.

Finally, the invention also has for an object to provide a method forthe removal of undesired contamination on a surface.

For these and other objects which will be clear from the following thepresent invention provides for a polysaccharide-based composition, saidcomposition comprising or essentially consisting of:

at least a first component a) excluding galactans constituted by asubstituted β-1,4 -linked galactan which is dissolvable in water of acertain temperature and which has a molecular weight (Mw) of ≧5·10⁴Daltons, preferably ≧10⁵ Daltons, particularly ≧10⁶ Daltons, and

at least a second component b) also excluding galactans, constituted bya substituted β-1,4 -linked glycan which is more difficult to dissolvethan said first component at said temperature, or is agar or acarrageenan.

In such composition it is preferred that component a) is a substitutedβ-1,4-linked glucan, glucomannan, xylan, mannan or a β1,4-linkedpolysaccharide consisting of 2-acetamido-2-deoxy-D-glucopyranos-or2-amino-2-deoxy-D-glucopyranos entities. The substitution of the glycanof component a) is preferably constituted by mono- or oligosaccharidegroups or hydroxyalkyl, carboxyalkyl, aminoalkyl, alkyl, acyl orhydroxyalkyl(alkyloxy)alkyl.

Component b) in the composition of the present invention is preferably asubstituted β-1,4-linked glucan, glucomannan, xylan, mannan or aβ1,4-linked polysaccharide consisting of2-acetamido-2-deoxy-D-glucopyranos-or 2-amino-2-deoxy-D-glucopyranosentities, or agar or carrageenan. The substitution of the glycan ofcomponent b) may be the same as that of component a).

In a preferred embodiment of the composition of this invention componentb) is a substituted β-1,4-linked glucan, glucomannan, xylan, mannan or aβ1,4-linked polysaccharide consisting of2-acetamido-2-deoxy-D-glucopyranos or 2-amino-2-deoxy-D-glucopyranosentities, or agar or carrageenan. The substitution consisting of mono-or oligosaccharide groups or hydroxyalkyl, carboxyalkyl, aminoalkyl,alkyl, acyl or hydroxyalkyl(alkyloxy)alkyl.

According to yet another embodiment of the invention component a) is asubstituted β-1,4-linked glucan or mannan, chitin or chitosan, componentb) also being a polysaccharide selected from these or from agar andcarrageenan. In such composition the substitution is preferably mono- oroligosaccharide groups, hydroxyalkyl, carboxyalkyl, alkyl, acyl orhydroxymethyl(methyloxy)methyl.

According to a particularly preferred embodiment of the inventioncomponents a) and b) are selected from galactomannans, cellulosederivatives, chitin derivatives and chitosan derivatives. In suchcomposition components a) and b) are suitably selected fromgalactomannans, hydroxyethyl cellulose and carboxymethyl celluloses.Components a) and b) are particularly selected from galactomannans, suchas Guar gums and Locust bean gums.

In regard to the character of components a) and b) as concerns theirdissolvability in water of a certain temperature, such temperature isnot critical as to its level but constitutes a demarcation line betweenthe two components in regard to dissolvability in water. However, fornormal uses of the composition of the present invention at normalenvironmental temperatures, a practical temperature range would be fromabut 30° C. to about 50° C. although still not a limiting range. Atnormal room temperature a practical demarcation temperature would beabout 40° C.

It is important to note that the composition of the invention whenpractically utilized is arranged in the form of a solid film, whereinthe polysaccharides are present in an essentially amorphous state.

The invention also covers within its scope a body in solid phase havinga surface intended for contact with a liquid and for relative movementbetween surface and liquid. Such surface is coated with a solid filmessentially consisting of a composition in accordance with the presentinvention.

The expression "a body in solid phase" as used herein is to be broadlyinterpreted to define definite shape and volume, but it should not beconstrued to exclude bodies which are hollowed out. Thus, the term"solid" merely defines a physical state as being neither liquid, norgaseous.

According to another aspect of the invention such coated surface facingthe film is provided with regularly or randomly distributed grooves orribs aligned in the flow direction of the relative movement between bodyand liquid.

According to another embodiment of the invention said film exposed tothe liquid is provided with regularly or randomly distributed grooves orribs aligned in the flow direction of said relative movement.

A primer may be placed between the surface and the film, and in thosecases where the surface is constituted by a plastic the primerpreferably comprises an albumin material.

Such body in solid phase is preferably constituted by a watercraft.

While applying the techniques of the present invention for reducingfriction or drag in a system where a body in solid phase moves through asurrounding liquid, mostly water, the polysaccharides contained in thefilm applied on to the body in question are released to the viscousboundary layer by dissolution in combination with diffusion from thefilm. The dissolved polysaccharides are primarily dissolved from thefilm and then diffused through the adhering viscous boundary layer outinto the mobile aqueous phase. Since, however, the diffusion rate of thepolysaccharides through the liquid is slow a relative high concentrationthereof can be maintained in a viscous boundary layer thereby providingthereat a friction- or drag-reducing effect.

In regard to this particular aspect of the invention it will be furtherdescribed in the following mainly in connection with application onwatercraft, i.e. solid bodies in contact with water, but it should beobserved that the applicability of the invention is in no way limitedthereto. Thus, it is conceivable to use the invention in allapplications where a solid body moves relative to a liquid, and theinvention is thus as concerns this application aspect thereof limitedonly to the extent defined by the appended patent claims.

In regard to the proportions between components a) and b) of thepolysaccharide-based composition of the invention, this proportion isnot critical as long as there are at least one component of each of thetypes a) and b) present in the composition. However, although theproportional ratio between same is not critical it is preferred that itlies within the range about 1:99 to 99:1, preferably from about 1:10 toabout 10:1.

In regard to the grooves or ribs that may be combined with theapplication of a film of a composition according to the invention thesemay in cross-section be of any shape, although from manufacturingreasons it is preferred that they in cross-section have an essentiallytriangular shape. In regard to the dimensions of such ribs or groovesquite generally both spacing and height lie within the range of about 25to about 250 microns. This dimensional range applies generally to wateras a liquid. At lower speeds, say 1 to 3 meters per second, spacing andhighest are selected from the upper part of this range, whereas athigher speeds, i.e. greater than about 3 meters per second, the lowerrange is preferred. In relation to liquids of higher viscosity thanwater the dimensional range of said ribs or grooves can extend up toabout 1,000 microns.

As indicated earlier such ribs or grooves may be arranged in theuncoated body before applying a solid film of the composition of theinvention, but it is also possible to arrange for ribs or grooves on theexposed side of the film.

As also indicted earlier in this disclosure the composition describedcan be used in other technical areas than as a means for reducingfriction. Thus, the composition can be used as a means for facilitatingremoval of undesired contamination from surfaces, such as graffiti,scrawl, soot, traffic contamination etc. This is an highly interestinguse of the composition described herein and it has been found to greatlyreduce or even eliminate the problem of the removal of contaminationfrom surfaces in public places, such as from underground cavities,trains, building facades etc.

In regard to this particular aspect of the invention there is provided amethod for the removal of such undesired contamination on a surface.Such method includes the steps:

a) spraying a solution of a composition on to said surface before it issubjected to contamination,

b) allowing the applied solution to dry to form a solid film,

c) wetting the coated surface, after contamination thereof, with aliquid, and

d) removing the undesired contamination by spraying, brushing, gentlerubbing or the like of the said surface with a liquid. The solution usedfor the cleaning procedure is preferably an aqueous one and likewise anaqueous liquid is preferably used for the wetting and cleaning steps.

Other conceivable uses for the composition of the present invention arei.a. use as a means for preserving moisture, use as a protective surfacecoverage, use as a packaging material and use as a slow release matrixor coating for drugs.

The polysaccharides used in the composition of the invention may be of asynthetic or natural character. Particularly preferred polysaccharidesare those originating from the plant kingdom.

Among such polysaccharides there may be mentioned saccharides derivedfrom plant materials, such as celluloses, pectines, and starch. Certainpolysaccharides may be used in a more or less native form, whereasothers, such as cellulose, may be used in more or less far-reachingsubstitutions for reaching suitable solubility properties. Another typeof plant polysaccharides are so called "gums" that may be constituted byalgyl constituents, carrageenans or extracts from plant seeds, such asGuar gum and Locust bean gum which is an extract of beads from Ceratoniasilique.

The film of polysaccharides can be applied to the body in any manner,for example by application of a liquid composition containing thepolysaccharide. The film formation can then take place after theapplication by for example drying, precipitation, polymerization or thelike. It is also conceivable to apply to the solid body the film in apre-fabricated form, the film being attached by gluing or the like.

When the film is formed in situ on the body it is suitable to apply tothe body in advance a suitable primer. Such primer can containmatrix-bound particles having affinity to the polymer, and as examplesof materials there may be mentioned activated carbon and albuminmaterials.

In regard to the practical use of the invention illustratingexemplification of varying uses will be made in the following. In regardto the use of the invention as a drag-reducing means reference is madeto the appended drawings, wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a diagram, wherein the traction force has been plotted as afunction of speed.

FIG. 2 is a vertical cross-section diagrammatically illustrating thetest rig used in the experiments,

FIG. 3 is an enlarged section along line II--II in FIG. 2; and

FIG. 4 shows a partial cross-section of the surface profile of a filmapplied to the hull of a boat model.

in the following specific examples the different solutions ofpolysaccharides were prepared in the following manner.

The respective polysaccharides in the form of dry powders are separatelytransferred to cold water (≦about 20° C.) under intense stirring and aredispersed to a fine suspension for about 10 minutes. The respectivemixtures are then heated to abut 40° C. (component a)) and about 90° C.(component b)), respectively, for a period of time of 30-45 minutes toobtain dissolution. The solutions are then allowed to cool down to roomtemperature under continued stirring and are then mixed to form thedesired polysaccharide-based composition ready for use.

In the examples below mixtures of two gums were used. The gums wereLocust bean gum sold by Sigma Chemical Corporation, St. Louis, USA. Thisgum is a galactomannan polysaccharide originating from seeds fromCeratonia siliqua. The other gum used was Guar gum from the samecompany.

The mixture used are designated in the example as "Composition" followedby a figure, where for example 20 means that 20% by weight of Guar gumand 80% by weight of Locust bean gum are contained in the mixture. Thefigure 30 means that 30% by weight of Guar gum are used in the mixture,the rest being Locust bean gum.

EXAMPLE 1

A sailboat hull of the boat type R-8 (1935) was used in the experiments.The data of this type of boat are waterline length 9.30 m, displacement8.5 tons and a wetted surface of about 20 m². The wetted area of thehull was initially coated with a primer consisting of carbon powder inthe form of activated carbon having a particle size of 20-50 microns andin a quantity of about 10% by weight in an epoxy base. After drying thecoated surface was carefully polished with fine sandpaper (No. 180)until an even and non-glossy surface was obtained. The surface waswashed with water for the removal of polishing particles.

For applying the technique of the present invention an aqueous solutionwas prepared containing 1% by weight of Composition 30. The surfaceprepared in advance with primer (activated carbon suspended in an epoxypaint, about 10% w/w) was then sprayed twelve times with this aqueoussolution with drying between each coating operation for about 1 hour. Intotal the surface was coated with 12 1 of aqueous solution. Afterconcluded coating the surface was then allowed to dry at 20° C. for 30hours, and the boat was then launched.

For carrying out traction tests the boat was towed using a motor-driventowboat in a protected harbor area while using a 25 m towline. Thetraction force in the towing was measured with a tensile tester coupledto an electronic recorder. Speed, wind velocity and wind direction weremeasured using modern electronic equipment (Danasystem 7000). Eachmeasurement was repeated twice with 180° change of towing direction.

The results obtained in these traction tests are shown on the appendedFIG. 1, wherein the traction force in kp at the vertical axis has beenplotted as function of speed in knots on the horizontal axis. Theexperimental results using the technique according to the invention isclear from curve a. The traction tests were repeated after 24 hours,essentially the same results being obtained.

The boat was then lifted ashore and a polysaccharide coating was removedusing a squirter and by scrubbing. The hull of the boat was then coatedwith a conventional Teflon-based hullpaint (VC17) and traction testswere performed again in the same manner as presented above. The resultsfrom these traction experiments are also presented in the appended FIG.1, by curve b.

As is clear from the displacement between the two curves there will beobtained by using the technique of this invention a substantialreduction of the drag due to reduced friction between boat hull andsurrounding water. The difference is obvious and statisticallysignificant.

EXAMPLES 2-4

The experiments presented under these examples were performed using thefriction test rig shown in FIGS. 2 and 3. The friction test riggenerally designated 1 comprises a header tank or funnel 3 having anupper cylindrical part 4 and a lower conical part 5.

The conical part 5 is at its lower end attached to a flow section 9,which is built up from test plates 11 of brass and side plates 13 toform a flow passage 15. The rig is furthermore provided with an outlet16,17 containing a control valve 19 for controlling liquid flow throughpassage 15.

All the elements described are supported by four support legs 7 standingon the ground, a platform or the like. Viewing windows 21,23 areprovided in the upper part of funnel 3 and the upper part of flowsection 9, respectively. These viewing windows have for their purpose toenable checking liquid levels in the test rig.

The friction test rig as described above is designed so that theturbulent friction qualities of various surface coatings can beconveniently assessed. The experimental results presented belowdemonstrate the fact that the test rig used gives reproducible resultswith water as at est fluid with and without approximately 10 ppm ofPolyox added to the water, the brass surfaces of test plates 11 beinguntreated. When Polyox is added to the water a marked increase of flowspeed occurs. The test rig described functions briefly as follows.

The apparatus is filled with the outlet valve 19 closed. The pressuretappings are connected to manometer tubes (not shown) and water suckedthrough to remove air bubbles. The flow is then started by a partial orcomplete opening of valve 19, and when the level passes the upper of thetwo marks 25 in the viewing upper window 21 a stopwatch is started.Marks 25 are 100 mm apart and when the level is approximately half waybetween them the manometer levels are read. The stopwatch is stoppedwhen the level in the header tank passes the lower mark.

Results obtained

According to H. Schlichting, "Boundary Layer Theory", p. 576, McGrawHill Book Company, New York, 1968, the pressure drop for turbulent flowthrough a given length of rectangular duct obeys the relation: ##EQU1##where U is mean flow speed

ρis fluid density

L is duct strength

d_(h) is hydraulic diameter, defined as 4 times cross sectionarea/wetted perimeter

R is Reynolds number Ud_(h/)γ, where

γis kinematic viscosity

and

K is a constant.

Kinematic viscosity depends somewhat on temperature, but for a narrowrange of temperatures this effect is negligible. For a 20 mm ×5 mm ductd_(h) =8 mm, whilst if the height h of the duct were reduced from 5 to 4mm, d_(h) would become 6^(2/3) mm. Thus the ratio of the d_(h) valueswould be 0.833, quite close to the ratio 0.8 of the h values. The valueof the constant K should change only slightly for changes in h of thisorder. The mean speed U is proportional to l/_(th), where t is the timefor given quantity of fluid to flow through the duct. Thus to a goodapproximation ##EQU2## where hs is the "standard" value of h as used inthe proving experiments. The results obtained bear this exception quiteaccurately, as can be seen from the following table.

    ______________________________________                                        Flow time t secs.                                                                          δp mm water                                                                           a       b                                          ______________________________________                                        101.3        965           5.14    -.02                                       100.5        978           5.14    -.02                                       100.2        1001          5.19    -.03                                        98.8        1029          5.20    -.04                                       109.5        843           5.14    -.02                                       113.2        803           5.17    -.01                                       110.0        841           5.16    0                                          107.4        846           5.06A                                              111.2        833           5.19    -.03                                       114.0        790           5.16    0                                          138.6        511           4.89B                                              110.7        831           5.16    0                                          116.2        767           5.17    -.01                                       110.7        828           5.15    -.01                                       223.2        236           5.07C                                              114.5        790           5.18    -.02                                       109.7        856           5.20    -.04                                       108.3        848           5.11    -.05                                       109.0        843           5.12    -.03                                       108.9        836           5.09    -.07                                       109.6        836           5.12    -.04                                       ______________________________________                                    

Clearly errors are possible due to inaccurate manometer readings which,since they change a little with time, must be taken at the appropriatehalf way time in each case. Such an error may account for the low valueof a at A. Also the R-1/4 law is probably not quite exact, so thesomewhat lower values of a at B and C (where the value was more closedthan in the other cases making the flow times correspondingly muchlonger), may in part be due to this. The mean of the rest of the valuesof a is 5.16 and the final column b of the table shows the differencesfrom this value, which in all cases except one lie within 1% of themean.

When approximately 10 ppm of Polyox was added to the Header tank watervery different values of a were obtained, as follows:

    ______________________________________                                        t               δp                                                                             a                                                      ______________________________________                                        104.5           757    4.62                                                   100.2           777    4.49                                                   ______________________________________                                    

Thus the apparatus is clearly able to demonstrate a large frictionreduction effect with such concentration of Polyox.

It should be noted that a flow time of 100 secs represents a flow speedthrough the duct of 2.5 m/s, similar to the speeds at which the 1/3scale 12 m yacht models are run, with similar values of turbulent skinfriction stress.

In the following examples the test rig described above has been used,the inside of brass plates 11 facing flow passage 15 being covered withthe gum mixtures used in the experiments. It is to be noted that thecoating thickness of the applied mixtures is not significant for thereduction of the friction as long as it lasts through the wholeexperiment. However, the approximate thickness of a layer swollen bycontact with water is of the order of a friction of a millimeter, but itmust be noted that the thickness per se is insignificant, as long as thecoating covers the surface contacting the liquid phase. (All percentagesrefer to weight.)

EXAMPLE 2 Test plates, Composition 20

Test plates 11 were coated with 9 layers of 0.5% Composition 20 withpaint brush. After each 3 layers of coat the plates were sanded(500/1200 paper).

The plates were allowed contact with water ˜10 min before Series 1 ofexperiments.

    ______________________________________                                        Series 1 (15-35 min)                                                          Flow time (s)   Sp (mm H.sub.2 O)                                                                        a                                                  ______________________________________                                        157.5           430        5.03                                               114.2           760        5.06                                               138.1           550        5.08                                               184.0           320        4.97                                               ______________________________________                                    

Average for a=5.035.

Average for volume measurements 92.5 ml (92.0, 93.0, 92.5).

Standard volume 92.0 ml gives a=5.16 for plain brass.

Corrected value for a=5.08.

Drag reduction (5.08/5.16)² =0.969 3.1%.

    ______________________________________                                        Series 2 (2 hrs-21.5 hrs)                                                     Flow time (s)   Sp (mm H.sub.2 O)                                                                        a                                                  ______________________________________                                        144.8           505        5.07                                               117.2           720        5.03                                               109.0           830        5.07                                               183.9           325        5.01                                               ______________________________________                                    

Average for a=5.045.

Average for volume=92.5 ml

Corrected value for a=5.09.

Drag reduction (5.09/5.16)² =0.973 2.7%.

    ______________________________________                                        Series 3 (20 hrs-20.30 hrs)                                                   Flow time (s)   Sp (mm H.sub.2 O)                                                                        a                                                  ______________________________________                                        115.5           775        5.17                                               144.6           515        5.12                                               140.4           540        5.11                                               153.0           465        5.11                                               106.0           885        5.12                                               ______________________________________                                    

Average for a=5.126.

Average for volume=92.75 ml.

Corrected value for a=5.19.

Drag reduction (5.19/5.16)² =1.0011%-1.1%.

    ______________________________________                                        Series 4 (30 hrs-30.15 hrs)                                                   Flow time (s)   Sp (mm H.sub.2 O)                                                                        a                                                  ______________________________________                                        111.0           820        5.13                                               135.1           575        5.10                                               175.3           365        5.10                                               114.0           760        5.04                                               121.5           685        5.07                                               ______________________________________                                    

Average for a=5.088.

Average for volume=92.75 ml.

Corrected value for a=5.16.

Drag reduction (5.16/5.16)² =1 0%.

Conclusion

The test surface showed a drag reduction of ˜3%. The surface waseliminated after 20 hrs and measurements at 20 hrs and 30 hrs showednormal values for uncoated surface. The plates were removed at 30 hrsand inspection showed absence of coating.

EXAMPLE 3 Test plates, Composition 30

Test plates 11 were coated with 9 layers of 0.5% Composition 30 withpaint brush. After each 3 layers of coat the plates were sanded(500/1200 paper).

The plates were allowed contact with water ˜10 min before Series 1experiments.

    ______________________________________                                        Series 1 (15-40 min)                                                          Flow time (s)   Sp (mm H.sub.2 O)                                                                        a                                                  ______________________________________                                        165.0           395        5.02                                               147.4           490        5.08                                               117.8           735        5.11                                               146.7           491        5.06                                               192.3           310        5.10                                               ______________________________________                                    

Average for a=5.074.

Average volume=92.0 ml.

Corrected value for a=5.07.

Drag reduction=3.5%.

    ______________________________________                                        Series 2 (1.30-1.45 hrs)                                                      Flow time (s)   Sp (mm H.sub.2 O)                                                                        a                                                  ______________________________________                                        182.8           335        5.07                                               127.2           640        5.10                                               112.1           805        5.13                                               122.1           690        5.12                                               ______________________________________                                    

Average for a=5.105.

Average volume=91.25 ml

Corrected value for a=5.03.

Drag reduction=5.0%.

    ______________________________________                                        Series 3 (2.30-2.45 hrs)                                                      Flow time (s)   Sp (mm H.sub.2 O)                                                                        a                                                  ______________________________________                                        121.0           705        5.13                                               148.0           495        5.08                                               147.7           490        5.08                                               136.8           570        5.13                                               ______________________________________                                    

Average for a=5.105.

Average volume=91.25 ml.

Corrected value for a=5.03.

Drag reduction=5.0%.

    ______________________________________                                        Series 4 (7-7.15 hrs)                                                         Flow time (s)   Sp (mm H.sub.2 O)                                                                        a                                                  ______________________________________                                        178.2           350        5.07                                               137.4           570        5.16                                               110.9           815        5.11                                               138.0           565        5.10                                               ______________________________________                                    

Average for a=5.095.

Average volume=91.25 ml.

Corrected value for a=5.02.

Drag reduction=5.2%.

    ______________________________________                                        Series 5 (10-10.30 hrs)                                                       Flow time (s)   Sp (mm H.sub.2 O)                                                                        a                                                  ______________________________________                                        164.8           405        5.09                                               115.8           770        5.17                                               177.1           365        5.16                                               144.0           530        5.13                                               ______________________________________                                    

Average for a=5.1375.

Average volume=91.0.

Corrected value for a=5.04.

Drag reduction=4.6%.

    ______________________________________                                        Series 6 (After 3 days)                                                       Flow time (s)   Sp (mm H.sub.2 O)                                                                        a                                                  ______________________________________                                        145.0           500        5.05                                               122.1           665        5.00                                               111.9           780        5.03                                               174.8           355        4.98                                               ______________________________________                                    

Average for a=5.02.

Average volume=93.5 (93, 94, 93.5, 93.5, 93, 94, 93).

Corrected value for a=5.16.

Drag reduction (5.16/5.16)² =1.00 0%.

EXAMPLE 4 Test plates, Composition 30

Test plates 11 were coated with 0.5% Composition 30 (20 layers withsanding (500/1200) in between every 3 layers). The plates were allowedcontact with water for ˜10 min before Series 1 of experiments.

    ______________________________________                                        Series 1 (15-40 min)                                                          Flow time (s)   Sp (mm H.sub.2 O)                                                                        a                                                  ______________________________________                                        161.2           415        5.05                                               135.0           550        4.97                                               127.0           635        5.07                                               149.2           460        4.95                                               119.5           695        5.02                                               173.0           350        4.92                                               ______________________________________                                    

Average for a=4.996.

Average for volume=92.5.

Corrected value for a=5.04.

Drag reduction (5.04/5.16)² =0.954 4.6%.

    ______________________________________                                        Series 2 (1 hr-1.20 hrs)                                                      Flow time (s)   Sp (mm H.sub.2 O)                                                                        a                                                  ______________________________________                                        149.8           465        5.00                                               109.7           800        5.00                                               112.8           760        4.99                                               133.5           585        5.08                                               137.5           545        5.03                                               114.2           750        5.04                                               ______________________________________                                    

Average for a=5.02.

Average for volume=92.0.

Corrected value for a=5.02.

Drag reduction (5.02/5.16)² =0.946 5.4%.

    ______________________________________                                        Series 3 (4 hrs-4.20 hrs)                                                     Flow time (s)   Sp (mm H.sub.2 O)                                                                        a                                                  ______________________________________                                        148.0           470        4.98                                               161.5           410        5.02                                               105.4           860        5.03                                               ______________________________________                                    

Average for a=5.01.

Average for volume=92.0.

Corrected value for a=5.01.

Drag reduction (5.01/5.16)² =0.942 5.8%.

    ______________________________________                                        Series 4 (10 hrs-10.30 hrs)                                                   Flow time (s)   Sp (mm H.sub.2 O)                                                                        a                                                  ______________________________________                                        145.0           510        5.11                                               118.0           725        5.09                                               158.9           420        5.02                                               107.6           855        5.10                                               169.3           380        5.05                                               ______________________________________                                    

Average for a=5.07.

Average for volume=92.0.

Corrected value for a=5.07.

Drag reduction (5.07/5.16)² =0.965 3.5%.

    ______________________________________                                        Series 5 (24 hrs-24.20 hrs)                                                   Flow time (s)   Sp (mm H.sub.2 O)                                                                        a                                                  ______________________________________                                        128.0           625        5.07                                               126.1           650        5.10                                               111.0           810        5.10                                               184.5           320         4.98*                                             ______________________________________                                    

Average for a=5.09 (* omitted).

Average volume=92.0.

Corrected value for a=5.09.

Drag reduction (5.09/5.16)² =0.973 2.7%.

    ______________________________________                                        Series 6 (26 hrs-27 hrs)                                                      Flow time (s)   Sp (mm H.sub.2 O)                                                                        a                                                  ______________________________________                                        134.1           580        5.08                                               119.0           730        5.15                                               126.9           650        5.14                                               176.1           370        5.16                                               127.0           650        5.14                                               119.0           725        5.13                                               ______________________________________                                    

Average for a=5.133.

Average for volume=92.0.

Corrected value for a=5.133.

Drag reduction=1.1%.

EXAMPLE 5

Tests were conducted at British Maritime Technology in the U.K. usingtheir No. 3 towing tank. A model yacht of approximately 6.4 m long wasused to assess its hydrodynamic resistance in the water with fourdifferent surface finishes on the hull--smooth painted surface,composition-coated surface, riblet-film surface and composition-coatedtable surface.

The composition used in these experiments was the same as that used inExample 1 above.

The resistance was measured using a dynamometer attached to the yacht asit was being towed through the calm water of the tank. The tests werecarried out at five different towing speeds ranging from 1.00 m/s to2.38 m/s. The riblet film had a semicircular cross section with a heightand rib spacing of about 125 μm and about 250 μm, respectively. FIG. 4shows a cross-section through such profiled film.

Results of the tests are given in Table 1 below in terms of theresistance coefficient C, which is linearly proportional to thehydrodynamic resistance at a given speed, percentage reduction comparedwith that of smooth painted surface is also given for each surfacefinish.

                  TABLE 1                                                         ______________________________________                                        Resistance coefficient (C × 10.sup.3 value) and percentage              reduction                                                                     in hydrodynamic resistance by using different hull-surface finishes           Surface finish                                                                                                    Composition                               Speed  Smooth   Composition Riblet  on Riblet                                 (m/s)  painted  Coated      Film    Film                                      ______________________________________                                        1.00   4.56     4.44        4.50    4.42                                                      (3.1%)      (1.8%)  (3.5%)                                    1.50   4.51     4.38        4.38    4.36                                                      (2.8%)      (2.8%)  (3.3%)                                    2.38   6.20     6.11        5.98    5.92                                                      (1.5%)      (3.5%)  (4.5%)                                    ______________________________________                                    

As can be seen from the table a significant reduction of the resistancecoefficient is obtained both by using the composition of the inventionand riblets, and that the combination of the two gives an even betterreduction of resistance. It can also be seen from the table that whereasa film of the composition of the invention has an effect which isreduced at increasing speed the riblets result in improved reduction ofresistance at increasing speed.

EXAMPLE 6

This example illustrates the use of the invention as a means forfacilitating removal of undesired contamination on a surface. In theexample there is used a polysaccharide solution containing about 2% byweight of Composition 30 as defend earlier in this disclosure. Thissolution is applied onto a smooth painted surface in several layers in aquantity of about 1 1 per m². The applied material is allowed to dry toa transparent film.

To imitate for example the graffiti problem the coated surface issubjected to scrawl using both a waterproof felt pen and a spray lacquerpaint. After the scrawl has dried the surface is cleaned using a spongesoaked in water. The contaminated surface is gently wiped using thesponge and the surface then becomes slippery and the contamination canbe easily washed away. After drying the film is reconstituted and theprocedure can be repeated several times with successful result in regardto the removal of the contamination. It goes without saying that thistechnique will highly facilitate the cleaning of contaminated surfacessince all materials used are non-toxic and since the removal procedureis quite simple to carry out using simple means of assistance.

EXAMPLE 7

This example is an illustration of the use of the inventive techniquesfor reducing friction in regard to plastic catheters for introductioninto a living animal body, such as the urinary tract. An ordinaryplastic catheter is used in the experiment and the surface thereof isintroductorily matted using wet-and-dry sanding (No. 1200 sandingpaper). The matted catheter is then dipped into a 1% by weight solutionof Composition 30, the procedure being repeated four times with dryingin between each dipping step.

Before use the treated catheter is soaked in water for one minute and isthen easily inserted due to its slippery surface. Again, in this use,the advantage of using the technique of the invention resides in thefact that the coating applied is non-toxic and can be reformed severaltimes.

EXAMPLE 8

This example illustrates the use of the invention for facilitating oraladministration of tablets.

Large aspirin tablets were dipped in a 1% by weight solution ofComposition 20 to produce a surface coating having a thickness ofapproximately 5-10 microns upon drying. When taken orally the tabletsbecome slippery when wetted in the mouth thus greatly facilitating theswallowing of same. This coating technique can be generally used due tothe non-toxicity of the composition used.

I claim:
 1. A friction reducing polysaccharide-based coating compositioncomprising:at least a first component a) excluding galactans comprisinga substituted β-1,4 -linked glycan which is dissolvable in water of acertain temperature and which has a weight average molecular weight (Mw)of ≧5·10⁴ Daltons, and at least a second component b) also excludinggalactans, comprising a substituted β-1,4 -linked glycan which is moredifficult to dissolve than said first component at said temperature, oris agar wherein the ratio between said first component and said secondcomponent is in a range sufficient to provide friction reducingproperties to said coating composition.
 2. A composition according toclaim 1, wherein component a) is a substituted β-1,4-linked glucan,glucomannan, xylan, mannan or a β1,4-linked polysaccharide consisting of2-acetamido-2-deoxy-D-glucopyranos-or 2-amino-2-deoxy-D-glucopyranosentities.
 3. A composition according to claim 1, wherein component b) isa substituted β-1,4-linked glucan, glucomannan, xylan, mannan or aβ1,4-linked polysaccharide consisting of2-acetamido-2-deoxy-D-glucopyranos-or 2-amino-2-deoxy-D-glucopyranosentities, or agar.
 4. A composition according to claim 2, whereincomponent b) is a substituted β-1,4-linked glucan, glucomannan, xylan,mannan or a β1,4-linked polysaccharide consisting of2-acetamido-2-deoxy-D-glucopyranos-or 2-amino-2-deoxy-D-glucopyranosentities.
 5. A composition according to claim 1, wherein component a) isa β-1,4-linked glycan substituted with mono- or oligosaccharide groupsor hydroxyalkyl, carboxyalkyl, aminoalkyl, alkyl, acyl orhydroxyalkyl(alkyloxy)alkyl.
 6. A composition according to claim 5,wherein component b) is a substituted β-1,4-linked glucan, glucomannan,xylan, mannan or a β1,4-linked polysaccharide consisting of2-acetamido-2-deoxy-D-glucopyranos-or 2-amino-2-deoxy-D-glucopyranosentities, or agar.
 7. A composition according to claim 1, whereincomponent b) is a β-1,4-linked glycan substituted with mono- oroligosaccharide groups or hydroxyalkyl, carboxyalkyl, aminoalkyl, alkyl,acyl or hydroxyalkyl(alkyloxy)alkyl or agar.
 8. A composition accordingto claim 2, wherein component b) is a β-1,4-linked glycan substitutedwith mono- or oligosaccharide groups or hydroxyalkyl, carboxyalkyl,aminoalkyl, alkyl, acyl or hydroxyalkyl(alkyloxy)alkyl, or agar.
 9. Acomposition according to claim 5, wherein component b) is a β-1,4-linkedglycan substituted with mono- or oligosaccharide groups or hydroxyalkyl,carboxyalkyl, aminoalkyl, alkyl, acyl or hydroxyalkyl(alkyloxy)alkyl, oragar.
 10. A composition according to claim 2, wherein component b) is asubstituted β-1,4-linked glycan which is more difficult to dissolve thansaid first component at said temperature, or is agar.
 11. A compositionaccording to claim 10, wherein component b) is a substitutedβ-1,4-linked glucan, glucomannan, xylan, mannan or a β1,4-linkedpolysaccharide consisting of 2-acetamido-2-deoxy-D-glucopyranos-or2-amino-2-deoxy-D-glucopyranos entities or agar.
 12. A compositionaccording to claim 10, wherein component b) is a β-1,4-linked glycansubstituted with mono- or oligosaccharide groups or hydroxyalkyl,carboxyalkyl, aminoalkyl, alkyl, acyl or hydroxyalkyl(alkyloxy)alkyl, oragar.
 13. A composition according to claim 1, wherein component b) is asubstituted β-1,4-linked glucan, glucomannan, xylan, mannan or aβ1,4-linked polysaccharide consisting of2-acetamido-2-deoxy-D-glucopyranos-or 2-amino-2-deoxy-D-glucopyranosentities, or agar, the substitution consisting of mono- oroligosaccharide groups or hydroxyalkyl, carboxyalkyl, aminoalkyl, alkyl,acyl or hydroxyalkyl(alkyloxy)alkyl.
 14. A composition according toclaim 2, wherein component b) is a substituted β-1,4-linked glucan,glucomannan, xylan, mannan or a β1,4-bound polysaccharide consisting of2-acetamido-2-deoxy-D-glucopyranos-or 2-amino-2-deoxy-D-glucopyranosentities, or agar, the substitution consisting of mono- oroligosaccharide groups or hydroxyalkyl, carboxyalkyl, aminoalkyl, alkyl,acyl or hydroxyalkyl(alkyloxy)alkyl.
 15. A composition according toclaim 5, wherein component b) is a substituted β-1,4-linked glucan,glucomannan, xylan, mannan or a β1,4-bound polysaccharide consisting of2-acetamido-2-deoxy-D-glucopyranos-or 2-amino-2-deoxy-D-glucopyranosentities, agar, the substitution consisting of mono- or oligosaccharidegroups or hydroxyalkyl, carboxyalkyl, aminoalkyl, alkyl, acyl orhydroxyalkyl(alkyloxy)alkyl.
 16. A composition according to claim 10,wherein component b) is a substituted β-1,4-linked glucan, glucomannan,xylan, mannan or a β1,4-linked polysaccharide consisting of2-acetamido-2-deoxy-D-glucopyranos-or 2-amino-2-deoxy-D-glucopyranosentities, or agar, the substitution consisting of mono- oroligosaccharide groups or hydroxyalkyl, carboxyalkyl, aminoalkyl, alkyl,acyl or hydroxyalkyl(alkyloxy)alkyl.
 17. A composition according toclaim 1, wherein component a) is a substituted β-1,4-linked glucan ormannan, chitin or chitosan, and wherein component b) also is apolysaccharide selected from these or from agar.
 18. A compositionaccording to claim 17, wherein the substitution is mono- oroligosaccharide groups, hydroxyalkyl, carboxyalkyl, aminoalkyl, alkyl,acyl or hydroxymethyl(methyloxy)methyl.
 19. A composition according toclaim 1, wherein components a) and b) are selected from galactomannans,cellulose derivatives, chitin derivatives and chitosan derivatives. 20.A composition according to claim 19, wherein components a) and b) areselected from galactomannans, hydroxyethyl celluloses and carboxymethylcelluloses.
 21. A composition according to claim 19, wherein componentsa) and b) are selected from galactomannans.
 22. A composition accordingto claim 21, wherein components a) and b) are selected from Guar gumsand Locust bean gums.
 23. The use of the composition according to claim1 as a means for reducing friction.
 24. A composition according to claim1 in the form of a solid film.
 25. A body in solid phase having asurface intended for contact with a liquid and for relative movementbetween surface and liquid, said surface being coated with a solid filmessentially consisting of a composition according to claim
 1. 26. A bodyaccording to claim 25, wherein said coated surfaces facing said film isprovided with regularly or randomly distributed grooves aligned in theflow direction of said relative movement.
 27. A body according to claim25, wherein said film exposed to the liquid is provided with regularityor randomly distributed grooves aligned in the flow direction of saidrelative movement.
 28. A body according to claim 25, wherein a primer isplaced between said surface and said film.
 29. A body according to claim28, wherein the surface is formed from a plastic and the primercomprises an albumin material.
 30. A body according to claim 25 which isconstituted by a water craft.
 31. The composition according to claim 1,wherein the ratio of said first component to said second component is inthe range of about 1:10 to about 10:1.
 32. The composition according toclaim 1, wherein the said first component comprises a substitutedβ-1,4-linked glycan having a weight average molecular weight of ≧10⁵Daltons.
 33. The composition according to claim 32, wherein said firstcomponent comprises a substituted β-1,4-linked glycan having a weightaverage molecular weight of ≧10⁶ Daltons.
 34. A method for reducingfriction, said method comprising applying to a body a compositioncomprisingat least a first component a) excluding galactans comprising asubstituted β-1,4 -linked glycan which is dissolvable in water of acertain temperature and which has a weight average molecular weight (Mw)of ≧5·10⁴ Daltons, and at least a second component b) also excludinggalactans, comprising a substituted β-1,4 -linked glycan which is moredifficult to dissolve than said first component at said temperature, oris agar or a carrageenan, wherein the ratio between said first componentand said second component is in a range sufficient to provide frictionreducing properties to said coating composition.
 35. A method forincreasing relative movement between a solid phase and a liquid, saidmethod comprising applying to a solid phase a composition comprisingatleast a first component a) excluding galactans comprising a substitutedβ-1,4 -linked glycan which is dissolvable in water of a certaintemperature and which has a weight average molecular weight (Mw) of≧5·10⁴ Daltons, and at least a second component b) also excludinggalactans, comprising a substituted β-1,4 -linked glycan which is moredifficult to dissolve than said first component at said temperature, oris agar or a carrageenan, wherein the ratio between said first componentand said second component is in a range sufficient to improve relativemovement between the solid phase and the liquid.